Tldr; take offer, don't quit engineering yet, you are fine

Don't quit engineering if you enjoy it. If you have better offer and the current ship is leaky as fuck => jump the ship. Saving the leaky ships should be very profitable if it is not => you are being heavily exploited.

I jumped the ship thrice. And one time accepted a lower payed position, just because I was quite burnout.

On the topic not using the progress and not understanding the Intenals. Understanding internal will not make you senior. Understanding what you can apply that you already know can make you senior. I remember being in a situation like yours. I thought I didn't know Jack, but then on a newplace I seen people who were running around like a headless chickens on crack. This has given me a good understanding about what knowledge is and that applicable knowledge is the key.